This invention concerns socket wrenches and more particularly, shield pieces for protecting decorative surface finishes from being marred during use of the socket wrenches.
In many instances, headed fasteners are provided with decorative surface finishes, such as the chrome plating of nut and bolt heads exposed to view to provide an aesthethic treatment. For example, auto wheel lug nuts are often exposed and chrome plated in sporty car models.
The pressure exerted in wrenching of such fasteners has a tendency to mar the finish, particularly in the instance of automotive wheel lug nuts, since the use of pneumatically driven tools increases the wrenching forces. Such pneumatic tools have come into widespread use in commercial tire and brake shops.
The end of the socket also mars the wheel surface as the nuts are wrenched tight, and the perimeter of the socket can mar closely adjacent finished wheel hubs by rubbing contact. Impacting of these surfaces also often inadvertently occurs, also resulting in damage to the decorative surfaces.
There has heretofore been provided cushioning inserts to reduce the incidence of marring of the nuts, as described in U.S. Pat. No. 3,433,108 issued to O. J. Ondeck on Mar. 18, 1969.
The insert described in the Ondeck patent comprises a short hollow cylinder mating with the inside of the socket wrench opening, the insert itself defining an inside opening mating with a hex fastener of a slightly smaller size than would otherwise be fit to the socket wrench. While such inserts do reduce the incidence of marring, the sockets can still mar the adjacent wheel and hub surfaces as the socket nut is wrenched on or off, and the pneumatic drives can destroy the insert after only a few uses.
The leading edge of the insert may be subjected to excessive pressure concentrations, tending to deform and loosen the insert, and the entire insert is easily dislodged unintentionally, particularly after extended use.
Since the insert of Ondeck only partially protects the surface, and has limitations when used with pneumatic tools, this design has not enjoyed widespread commercial success.
The Ondeck patent describes inserts made of Delrin and other plastics, which is satisfactory for manual wrenching, but which does not stand up in use with power tools.
The use of any plastic material as a wrench liner for short height nuts tends to result in splitting of the liner due to compressive stresses exerted by the wrenching process.